Systems and methods herein generally relate to printers and printer systems, and more particularly to creating bitmaps used in printing.
Halftoning techniques are widely employed in the printing and display of digital images, and are used because the physical processes involved are binary in nature or because the processes being used have been restricted to binary operation for reasons of cost, speed, memory, or stability in the presence of process fluctuations. The term halftoning refers to a process of representing an image as a bi-level image such that, when viewed from a suitable distance, it gives the same impression as the original image. Halftoning reduces the number of quantization levels per pixel in a digital image. Over the long history of halftoning, a number of halftoning techniques have been developed which are adapted for different applications.
Classical halftone screening applies a mask of threshold values to each color of the multi-bit image. Such thresholds are stored as a matrix in a repetitive pattern. Each tile of the repetitive pattern of the matrix is a halftone cell. Digital halftones generated using threshold arrays that tile the image plane were originally designed to be periodic for simplicity and to minimize memory requirements. With the increase in computational power and memory, these constraints become less stringent. Digital halftoning uses a raster image or bitmap within which each monochrome picture element or pixel may be on or off (ink or no ink). Consequently, to emulate the photographic halftone cell, the digital halftone cell contains groups of monochrome pixels within the same-sized cell area.
To keep the same appearance at each color level, the halftone dot sizes used are smaller, and the amount of toner used is smaller. An issue with high frequency or stochastic screens is that they can appear unstable or noisy when used in laser printers. If the pattern is stochastic with irregular spacing between the dots, the appearance can be quite noisy.